Bài giảng Well drilling engineering - Chapter 4: Rolling Cutter Bits (Part 2) - Đỗ Quang Khánh

1 Well Drilling Engineering Rolling Cutter Bits Dr. DO QUANG KHANH 2 Lesson 8 - Bits cont’d Rolling Cutter Bits Steel Tooth (milled tooth) Carbide Tooth (tungsten carbide insert - TCI) Grading of Worn Bits Bit Performance Buoyancy 3 Read:   Applied Drilling Engineering, Ch.5 (bits) HW #: ADE 1.18. 1.19, 1.24 4 Tungsten Carbide Insert Bit Milled Tooth Bit 5 6 Rotary Drill Bits Roller Cutter Bits - rock bits First rock bit introduced in 1909 by Howard Hughes 2 - cone bit Not self - cleaning 7 Rotary Drill Bits Improvements 3 - cone bit (straighter hole) Intermeshing teeth (better cleaning) Hard - facing on teeth and body Change from water courses to jets Tungsten carbide inserts Sealed bearings Journal bearings 8 Rotary Drill Bits Advantages For any type of formation there is a suitable design of rock bit Can handle changes in formation Acceptable life and drilling rate Reasonable cost 9 Fluid flow through water courses in bit Proper bottomhole cleaning is very important 10 Fluid flow through jets in the bit (nozzles) 11 Rotary Drill Bits Milled Tooth Bit (Steel Tooth) Long teeth for soft formations Shorter teeth for harder formations Cone off - set in soft - formation bit results in scraping gouging action Self - sharpening teeth by using hardfacing on one side High drilling rates - especially in softer rocks 12 Milled Tooth Bit (Steel Tooth) 13 Rotary Bits Tungsten Carbide Insert Bits Long life cutting structure in hard rocks Hemispherical inserts for very hard rocks Larger and more pointed inserts for softer rock Can handle high bit weights and high RPM Inserts fail through breakage rather than wear (Tungsten carbide is a very hard, brittle material) 14 Tungsten Carbide Insert Bits 15 Sealed Bearing Lubrication System 16 Sealed, self-lubricated roller bit journal bearing design details INSERTS SILVER PLATED BUSHING RADIAL SEAL BALL BEARING GREASE RESERVOIR CAP BALL RETAINING PLUG BALL RACE 17 Roller Cone Bearings 18 Bearings Ball Bearings (point contact) Roller Bearings (line contact) Journal bearing (area contact) Lubrication by drilling fluid . . . or . . . 19 Bearings Journal Bearings (area contact) Wear - resistant hard surface on journal Solid lubricant inside cone journal race O - ring seal Grease Sealed Bearings (since 1959) Grease lubricant (much longer life) Pressure surges can cause seal to leak! Compensate? 20 Grading of Dull Bits  How do bits wear out? Tooth wear or loss Worn bearings Gauge wear 21 Grading of Dull Bits How do bits wear out? Steel teeth - graded in eights of original tooth height that has worn away e.g. T3 means that 3/8 of the original tooth height is worn away 22 Grading of Dull Bits Broken or Lost Teeth Tungsten Carbide Insert bit e.g. T3 means that 3/8 of the inserts are broken or lost 23 Grading of Dull Bits How do bits fail? Bearings: B3 means that an estimated 3/8 of the bearing life is gone Balled up Bit Cracked Cone 24 Grading of Dull Bits How do bits fail? Washed out Bit Lost Cone 25 Grading of Dull Bits How do bits wear out? Examples: T3 – B3 - I T5 – B4 - 0 1/2 Gauge Wear: Bit is either in - Gauge or out - of - Gauge Measure wear on diameter (in inches), using a gauge ring BIT GAUGE RING 26 IADC ROLLER CONE BIT CLASSIFICATION SYSTEM 27 IADC System Operational since 1972 Provides a Method of Categorizing Roller Cone Rock Bits Design and Application related coding Most Recent Revision ‘The IADC Roller Bit Classification System’ 1992, IADC/SPE Drilling Conference Paper # 23937 28 IADC Classification 4-Character Design/Application Code First 3 Characters are NUMERIC 4 th Character is ALPHABETIC 135M or 447X or 637Y 29 Examples 637Y medium-hard insert bit; friction bearing with gage protection; conical inserts 135M soft formation Milled tooth bit; roller bearings with gage protection; motor application 447X soft formation insert bit; friction bearings with gage protection; chisel inserts 30 Sequence Numeric Characters are defined: Series 1 st Type 2 nd Bearing & Gage 3 rd Alphabetic Character defined: Features Available 4 th 135M or 447X or 637Y 31 Series FIRST CHARACTER General Formation Characteristics Eight (8) Series or Categories Series 1 to 3 Milled Tooth Bits Series 4 to 8 Tungsten Carbide Insert Bits The higher the series number, the harder/more abrasive the rock 1 35M or 4 47X or 6 37Y 32 Define Hardness 33 Type SECOND CHARACTER Degree of Hardness Each Series divided into 3 or 4 ‘Types’ Type 1 Softest Formation in a Series Type 4 Hardest Formation in a Series Increasing Rock Hardness 1 3 5M or 4 4 7X or 6 3 7Y 34 Bearing & Gage THIRD CHARACTER Bearing Design and Gage Protection Seven (7) Categories 1. Non-Sealed (Open) Roller Bearing 2. Roller Bearing Air Cooled 3. Non-Sealed (Open) Roller Bearing Gage Protected 4. Sealed Roller Bearing 5. Sealed Roller Bearing Gage Protected 6. Sealed Friction Bearing 7. Sealed Friction Bearing Gage Protected 13 5 M or 44 7 X or 63 7 Y 35 Features Available FOURTH CHARACTER Features Available (Optional) Sixteen (16) Alphabetic Characters Most Significant Feature Listed (i.e. only one alphabetic character should be selected). 135 M or 447 X or 637 Y 36 IADC Features Available A - Air Application B - Special Bearing/Seal C - Center Jet D - Deviation Control E - Extended Nozzles G - Gage/Body Protection H - Horizontal Application J - Jet Deflection L - Lug Pads M - Motor Application S - Standard Milled Tooth T - Two-Cone Bit W - Enhanced C/S X - Chisel Tooth Insert Y - Conical Tooth Insert Z - Other Shape Inserts 135 M or 447 X or 637 Y 37 Categorization - Summary Convenient Categorization System Design and Application Code Know its Limitations Use Carefully in Application Decisions Consider other sources: offset bit records; dull grading; performance analysis. 38 39 A “D” in front signifies a diamond bit D1 - D5 signifies a natural diamond or PDC bit D7 - D9 signifies a natural diamond or PDC core bit 40 How to Improve Bit Performance 1 . Stabilize the bit 2. Maintain minimum mud weight, sand and solids 3. Maintain adequate bottom hole cleaning 4. Protect the seals - avoid pressure surges 5. Thoroughly inspect bit before re-running 6. Keep oil from the mud, and from the seals 7. Follow manufacturers recommendations (e.g. 6,000 lb/in of diameter and 40-60 RPM ) 41